Workpiece surface influencing device designs for electrochemical mechanical processing and method of using the same

ABSTRACT

The present invention is directed to a top surface of a workpiece surface influencing device and a method of using the same. The top surface of the workpiece surface influencing device is adapted for use in an electrochemical mechanical processing apparatus in which a solution becomes disposed onto a conductive surface of a workpiece and electrochemical mechanical processing of the conductive surface is performed while relative movement and physical contact exists between the top surface and the conductive surface. The top surface comprises a ceramic material that presents a substantially planar contact area to the conductive surface, the ceramic material having a hardness greater than that of the conductive surface. A plurality of channels are formed through the top surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/302,755, filed Nov. 21, 2002, now U.S. Pat. No. 7,204,917, whichclaims priority to U.S. Provisional Application No. 60/331,783 filedNov. 21, 2001. U.S. patent application Ser. No. 10/302,755 is acontinuation-in-part of U.S. patent application Ser. No. 10/165,673filed Jun. 6, 2002, now U.S. Pat. No. 6,837,979, which is a divisionalof U.S. patent application Ser. No. 09/373,681, filed Aug. 13, 1999, nowU.S. Pat. No. 6,409,904, which is a continuation-in-part application ofU.S. patent application Ser. No. 09/201,929, filed Dec. 1, 1998, nowU.S. Pat. No. 6,176,992, and U.S. patent application Ser. No.09/285,621, filed Apr. 3, 1999, now U.S. Pat. No. 6,328,872. Thedisclosures of the foregoing applications and patents are herebyincorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to manufacture of semiconductor integratedcircuits and, more particularly to a method for planar deposition oretching of conductive layers.

BACKGROUND OF THE INVENTION

Conventional semiconductor devices generally include a semiconductorsubstrate, usually a silicon substrate, and a plurality of sequentiallyformed dielectric interlayers such as silicon dioxide and conductivepaths or interconnects made of conductive materials. Copper and copperalloys have recently received considerable attention as interconnectmaterials because of their superior electromigration and low resistivitycharacteristics. The interconnects are usually formed by filling copperin features or cavities etched into the dielectric interlayers by ametallization process. The preferred method of copper metallizationprocess is electroplating. In an integrated circuit, multiple levels ofinterconnect networks laterally extend with respect to the substratesurface. Interconnects formed in sequential interlayers can beelectrically connected using vias or contacts.

In a typical process, first an insulating interlayer is formed on thesemiconductor substrate. Patterning and etching processes are performedto form features such as trenches and vias in the insulating layer.Then, copper is electroplated to fill all the features. However, theplating process results in a thick copper layer on the substrate some ofwhich need to be removed before the subsequent step. Conventionally,after the copper plating, CMP process is employed to globally planarizeor reduce the thickness of the copper layer down to the level of thesurface of the insulation layer. However, CMP process is a costly andtime consuming process that reduces production efficiency.

The adverse effects of conventional material removal technologies may beminimized or overcome by employing an Electrochemical MechanicalProcessing (ECMPR) approach that has the ability to provide thin layersof planar conductive material on the workpiece surface, or even providea workpiece surface with no or little excess conductive material. Theterm of Electrochemical Mechanical Processing (ECMPR) is used to includeboth Electrochemical Mechanical Deposition (ECMD) processes as well asElectrochemical Mechanical Etching (ECME), which is also calledElectrochemical Mechanical Polishing. It should be noted that in generalboth ECMD and ECME processes are referred to as electrochemicalmechanical processing (ECMPR) since both involve electrochemicalprocesses and mechanical action.

FIG. 1 shows an exemplary conventional ECMPR system 2, which system 2includes a workpiece-surface-influencing device (WSID) 3 such as a mask,pad or a sweeper, a carrier head 4 holding a workpiece 5 and anelectrode 6. The workpiece-surface-influencing-device (WSID) is usedduring at least a portion of the electrotreatment process when there isphysical contact or close proximity and relative motion between theworkpiece surface and the WSID. Surface of the WSID 3 sweeps the surfaceof the workpiece 5 while an electrical potential is established betweenthe electrode 6 and the surface of the workpiece. Channels 7 of the WSID3 allow a process solution 8 such as an electrolyte to flow to thesurface of the workpiece 5. If the ECMD process is carried out, thesurface of the workpiece 5 is wetted by a deposition electrolyte whichis also in fluid contact with the electrode (anode) and a potential isapplied between the surface of the workpiece and the electrode renderingthe workpiece surface cathodic. If the ECME process is carried out, thesurface of the workpiece 5 is wetted by the deposition electrolyte or aspecial etching electrolyte, which is also in fluid contact with anelectrode (cathode) and a potential is applied between the surface ofthe workpiece and the electrode rendering the workpiece surface anodic.Thus etching takes place on the workpiece surface. Very thin planardeposits can be obtained by first depositing a planar layer using anECMD technique and then using an ECME technique on the planar film inthe same electrolyte by reversing the applied voltage. Alternately, theECME step can be carried out in a separate machine and a differentetching electrolyte. The thickness of the deposit may be reduced in aplanar manner.

Descriptions of various planar deposition and planar etching methodsi.e. ECMPR approaches and apparatus can be found in the followingpatents and pending applications, all commonly owned by the assignee ofthe present invention. U.S. Pat. No. 6,126,992 entitled “Method andApparatus for Electrochemical Mechanical Deposition.” U.S. applicationSer. No. 09/740,701 entitled “Plating Method and Apparatus that Createsa Differential Between Additive Disposed on a Top Surface and a CavitySurface of a Workpiece Using an External Influence,” filed on Dec. 18,2001, and application Ser. No. 09/169,913 filed on Sep. 20, 2001,entitled “Plating Method and Apparatus for Controlling Deposition onPredetermined Portions of a Workpiece”. These methods can deposit metalsin and over cavity sections on a workpiece in a planar manner. They alsohave the capability of yielding novel structures with excess amount ofmetals selectively over the features irrespective of their size, ifdesired.

The surface of the WSID preferably contains hard-abrasive material forefficient sweeping. U.S. application Ser. No. 09/960,236 filed on Sep.20, 2001, entitled “Mask Plate Design,”,U.S. Provisional ApplicationSer. No. 60/326,087 filed on Sep. 28, 2001, entitled “Low ForceElectrochemical Mechanical Processing Method and Apparatus,” and U.S.application Ser. No. 10/155,828 filed May 23, 2002, all of which areassigned to the same assignee as the present invention, disclose variousworkpiece-surface-influencing device embodiments.

Fixed abrasive sheets or pads, which are supplied by companies such as3M and which are commonly used in CMP applications, work efficiently onWSID surfaces. Such abrasive sheets are generally comprised of abrasivecomposites that have a discernible precise shape such as pyramidal orcylindrical. The abrasive composite shapes include a plurality ofabrasive grains dispersed in a binder that also bonds abrasive compositeshapes to a backing. During a CMP process, as the abrasive sheet isbeing used to abrade a surface, the abrasive composite shapes break downand expose unused abrasive grains embedded in the binder. As the sheetis used for an extended time period, the composite shapes further breakdown and expose more abrasive grains. For an ECMPR process, due to theconstant breaking down of the abrasive layer, such abrasive sheets haverelatively short life time and need to be replaced often. This in turnlowers throughput and also adversely affect product consistency.

Therefore, it will be desirable to provide a longer life abrasive andhard surface for the WSID used in an ECMPR technique.

SUMMARY OF THE INVENTION

The present invention is directed to a top surface of a workpiecesurface influencing device and a method of using the same. The topsurface of the workpiece surface influencing device is adapted for usein an electrochemical mechanical processing apparatus in which asolution becomes disposed onto a conductive surface of a workpiece andelectrochemical mechanical processing of the conductive surface isperformed while relative movement and physical contact exists betweenthe top surface and the conductive surface. The top surface comprises aceramic material that presents a substantially planar contact area tothe conductive surface, the ceramic material having a hardness greaterthan that of the conductive surface. A plurality of channels are formedthrough the top surface.

In one aspect, the substantially planar contact area includes aplurality of contact regions, each of the contact regions including aregion top surface that is substantially planar with other region topsurfaces. These plurality of contact regions may each be raised above alayer disposed below, which layer may be another ceramic material, or ametal that can be used as an anode or a cathode. Each of the pluralityof contact regions will have an associated region top surface, which maybe flat, rounded, triangular or some other shape, such that the topportion of each of the region top surfaces together form a substantiallyplanar contact area.

In another embodiment each of a plurality of contact regions is formedas a separable sweep element, thereby resulting in a plurality ofseparable sweep elements. The separable sweep elements can have a regiontop surface that is flat, rounded, triangular, or some other shape.Further, the sweep elements may include drain channels, particularly onthe leading edge of the sweep element.

The method according to the present invention provides forelectrochemical mechanical processing of a conductive surface of aworkpiece using a workpiece surface influencing device as describedabove and hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts an ECMPR system;

FIG. 2 schematically depicts a portion of an ECMPR system using anembodiment of a WSID of the present invention;

FIG. 3 schematically depicts a planar view of an embodiment of a WSID ofthe present invention;

FIG. 4 schematically depicts a side cross section of an embodiment of aWSID of the present invention;

FIG. 5A schematically shows sweep elements in conjunction with the WSIDaccording to the present invention;

FIGS. 5B-5H schematically shows cross-sectional views of variousembodiments of the sweep elements and drain channels according to thepresent invention;

FIG. 5I schematically shows a perspective view of a sweep element anddrain channel according to the present invention;

FIGS. 6A to 6D schematically show a method of making an embodiment of aWSID of the present invention;

FIG. 6E schematically shows an alternative step in method of making aWSID of the present invention; and

FIG. 7 schematically depicts a planar copper layer formed on a surfaceof a workpiece using the WSID of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In one embodiment, a workpiece surface influencing device (WSID) of thepresent invention includes a pattern of raised regions that provides alonger life cycle when compared to a conventional WSID. As used herein,the terms “workpiece surface,” “wafer surface” and the like include, butare not limited to, the surface of the work piece or wafer prior toprocessing and the surface of any layer formed thereon, includingoxidized metals, oxides, spun-on glass, ceramics, etc.

Reference will now be made to the drawings wherein like numerals referto like parts throughout. FIG. 2 schematically depicts one embodiment ofa WSID of the present invention, which WSID is placed in close proximityof a workpiece 11, such as a wafer, having a surface 12 to be plated.

The WSID may include a body 13 having a plurality of raised regions 14and recessed regions 18 distributed on an upper surface of the WSID body13. Recessed regions 18 are surface channels extending along the surface15 of the WSID body 13. A top surface 19 of the raised regions 14 sweepsthe wafer surface 12 during the process. The WSID body 13 may beconstructed of more than one layer. Preferably, the body 13 is comprisedof materials that are non-reactive with the deposited or etched metallayer and the process solution that is used. Thus, the body 13 may beone of a reinforced or pure polymeric material, a metallic material, aceramic material, a glass material, and mixtures thereof. Usefulpolymeric materials include polypropylene and polyvinyl chloride (PVC).Metallic materials can include titanium, tantalum, or their platinumcoated versions. The WSID body 13 can also be an electrode for examplean anode for the above described ECMD processes and a cathode for theabove described ECME processes. In such case, parts of the WSID bodythat may contact the workpiece can be coated with an insulator layer, orthe raised regions can be made of insulating materials. Irrespective ofwhether the body 13 is an electrode or just a support element for theraised regions, the WSID body 13 preferably includes a plurality ofopenings or channels 17. Channels 17 communicate electrolyte between anelectrode (not shown) and the wafer surface 12 on which a metal layer,preferably copper layer, may be deposited (See also FIG. 1). Channels 17are connected to the recessed regions 18 and may have the same width andlength as the recessed regions 18. The plurality of raised regions 14may be an integral part of or non-separable from the body 13. Thus, theraised regions 14 may comprise the same material as the body 13.Additionally, the plurality of raised regions 14 is preferably disposedin a pattern, and the recessed regions 18 continue among them. Whileeach of the raised regions 14 is illustrated as being of the same sizeand configuration, the present invention contemplates that the raisedregions 14 may be constructed with differing sizes and configurations.In general, the raised regions 14 and in particular the top surface 19of the raised regions, may serve to sweep the electrolyte across thewafer surface 12 as well as polish the wafer surface 12. As with theraised regions 14, the recessed regions 18 among the raised regions maybe constructed with the same or differing sizes and configurations.

FIG. 3 schematically shows a top view of an exemplary embodiment of aWSID 40 with a pattern of raised regions 42 together with recessedregions 44 and channels 46 or holes. While FIG. 3 shows the patterns ofraised regions 42 and recessed regions 44 in a regular sequence, thescope of the present invention also includes a pattern of an irregularsequence. In FIG. 3, the raised regions 42 may be in the shape of ribsor blades. The raised regions 42 may also have a triangular crosssection (not shown). Between the raised regions 42 may be a plurality ofrecessed regions 44 connected to the channels 46.

As shown in FIG. 4, in another embodiment, which schematically depicts aside cross sectional view of a portion of a WSID 30. The WSID 30 mayinclude a top surface 29. In this embodiment, an outer layer 31 isformed on and conformally coats and the top surface 29 and hence theraised and recessed regions 14, 18. As will be described below, theouter layer may 31 be made of an insulating material. As seen in FIG. 4,the outer layer 31 may have openings 32 to enable the electrolyte toflow between the channels 17 and the recessed regions 18.

Optionally, and as shown in FIG. 5A, top of the WSID 30 may furtherinclude a plurality of surface features 34 or sweep elements integratedand/or separable from the WSID 30. The sweep elements 34 can help sweepthe electrolyte from the work piece surface 12 (see FIG. 2). The sweepelements 34 may also be integrated into and/or separable from the raisedregions 14. In other words, the plurality of sweep elements 34 may beremovable, replaceable, and/or re-buildable as needed. For example, thesweep elements 34 may be placed into or held in place by grooves 35formed in the WSID body 13 or in the raised regions 14. When the sweepelements 34 are worn, they can be replaced by a new set of sweepelements 34 (such as with a cartridge of sweep elements). Replacement ofthem can be performed by sliding the sweep elements 34 into the grooves35. Accordingly, the sweep elements 34 may be made of titanium, titaniumoxide, aluminum oxide, polyamides, epoxies, reinforced structuralpolymers or ceramics or various combinations. The sweep elements may beof various configurations, such as that shown in FIG. 5B, to cooperatewith the raised regions 14 in sweeping process solution across and fromthe wafer surface 12. A useful dimension for the sweep element 34 isbetween about 0.1 micron to 20 mm.

The sweep elements 34 may also contain channels 34 a for drainingelectrolyte off the surface 12 of the work piece 11 (FIG. 2). Also, thechannels 34 a can enhance fluid mixing or transfer within the fluidboundary layer regions between the sweep elements 34 and work piece 11(FIG. 2). Concurrently, the affected electrolyte is prevented fromaccumulating in front of the sweep elements 34 by draining through thechannels 34 a. Thus, the channels 34 a enhances mass transfer at thework piece interface and help reduce the accumulation of electrolyte inthe work piece interface during the sweeping action. The channels 34 ain the sweep elements may be of various configurations, such ascircular, rectangular, and triangular. Regardless of the shape of thechannels 34 a, the channels may be spread from one another by around 2to 5 mm. The drain channels 34 a of the sweep elements 34 may beparallel or inclined to the leading edge of the sweep elements 34. Therelative position of the channels 34 a and their orientation is suchthat they can maximize the preferential deposition of high quality metalin the various features or cavities (see FIG. 7) in the work piece 11.

In making the WSID 30, FIGS. 6A to 6D schematically depict one preferredmethod. In FIG. 6A, the WSID body 13 may initially be patterned by oneof a photolithographic method and/or a masking method. While theforegoing methods are preferred due to manufacturing ease, conventionalmachining, laser ablation, or water jet material fabrication methods mayalso be used. Either of the foregoing preferred methods can employconventional techniques to produce a patterned mask 22 on the topsurface 29 of the WSID body 13. The patterned mask 22 preferablyprovides a pattern that matches the pattern of raised regions 14 thatwill eventually be produced on the top surface 29.

Next, as shown in FIG. 6B, exposed portions 29 a of the top surface 29can be etched so as to produce relief structures 23 that may become theeventual recessed regions 18. Thereafter, the patterned mask 22 may beremoved by conventional methods; thereby leaving the raised regions 14and the recessed regions 18 integrated onto the top surface 29, as shownin FIG. 6C.

In FIG. 6D, the outer layer 31 or an insulating layer, which is alsoshown in FIG. 4, may be formed on the exposed surfaces of the raised andrecessed regions using methods such as anodization, sputtering, spincoating, and baking. The insulating layer 31 is a hard material andserves to polish the workpiece surface 12 (see FIG. 2) as it is plated.The layer 31 protects the WSID 30 and provides electrical insulation forit when contact is made with the workpiece surface 12. Accordingly, theinsulating layer 31 may be made of A1.sub.2O.sub.3, SiN, TiO.sub.2, orother ceramics, and particulate reinforced chemical resistant polymersand mixtures thereof, and produced by well-known methods such asdipping, spin coating, spraying and sputtering. In a specific example,the insulating layer 31 may be fabricated by anodizing the exposedsurfaces of raised and recessed regions 14, 18. For example the WSIDmaybe made of Ti or Ta and the surface may be anodized to obtain aprotective hard layer of Ti-oxide or Ta-oxide. Referring to FIG. 6D, inanother specific example, if the WSID body 13 is made of a hardpolymeric material such as a polycarbonate or high density polyethylene,the layer 31 can be formed as a hard coating or an abrasive surface. Inthis case abrasiveness of the layer 31 can be controlled by selectingmaterials from different friction coefficients. For example, if thecoating include alumina it will be hard and abrasive. If it includesdiamond like carbon coating, it will be hard but less abrasive becausesuch coatings are more slippery. Best abrasive coating can be selectedby selecting the coating without changing the shape of the surface ofthe WSID.

Following the formation of the insulating layer 31, the channels 17 maybe formed by machining the channels through the WSID 30. The channelsmay be formed by various methods such as drilling, electro etching, wetetching, laser ablation, water jet cutting, etc.

Alternatively, the insulating layer 31 may be formed after the openings32 are formed, thereby producing an insulating layer 31 not only overthe raised and recessed regions 14, 18 but also over the walls of thechannels 17, as shown in FIG. 6E. In another embodiment, the initialtopography of the WSID structure, including the raised regions 14, thechannels 17 and recessed regions 18, may be fabricated by mechanicallymachining the WSID. Thereafter, the structure's surface can beselectively anodized or spin coated with a suitable insulating, abrasiveor electrolyte sweeping elements or devices.

In view of the above, it can be seen that the present invention canprovide a way of rebuilding of a plurality of newer raised regions andrecessed regions after the raised regions in use are worn. In otherwords, a second plurality of raised regions and recessed regions areproduced by reprocessing the used WSID. Such rebuilding can beaccomplished by removing the worn raised regions or surface, such as bywet etch methods, oxygen plasma, or machine resurfacing. Thereafter, newor second raised regions are reformed, such as by anodizing the preparedsurface or spin coating on the prepared surface. Although not necessary,a reformed or second mask may correlate to the prior pattern of raisedregions and recessed regions. The exposed areas of the second mask maythen be insulated or anodized with another insulating or anodized layer.The entire WSID may be then annealed to toughen the WSID 30, and improveits chemical resistance to various electrolytes.

Whichever particular embodiment of the WSID 10, WSID 30 or method of thepresent invention is employed, FIG. 7 schematically depicts a portion 50of the workpiece 11, shown in FIG. 2, on which a planar metal layer 28,a copper layer, produced using the ECMPR. The planar metal layer 28 isformed on the workpiece by filling features or cavities such as vias 51and trenches 52 formed through an insulating layer 33. Conventionally, abarrier layer 26, preferably a Ta or TaN layer and a seed layer 27,preferably a thin copper layer are coated over the insulating layer 33having the features 51, 52 before the copper plating of the workpiece.The WSID of the present invention may be used to remove, i.e., etch orelectro-etch or electro-polish as in the CMP of copper on a wafer or asubstrate.

It should be understood, of course, that the foregoing relates topreferred embodiments of the invention and that modifications may bemade without departing from the spirit and scope of the invention.

1. A method of electrochemical mechanical processing a conductivesurface of a workpiece using a solution, comprising: disposing thesolution onto the conductive surface of the workpiece; electrochemicallymechanically processing the conductive surface in the presence of thesolution while relative movement and physical contact exists between atop surface of a workpiece surface influencing device and the conductivesurface, wherein the top surface of the workpiece surface influencingdevice is a ceramic material that presents a substantially planarcontact area to the conductive surface, the contact area including aplurality of contact regions formed over a conducting material havingrecessed and raised regions, and wherein a plurality of channels areformed through the top surface through which the solution passes,wherein each of the plurality of contact regions is formed over theconducting material as a separable sweeper; and inserting each separablesweeper into the workpiece surface influencing device prior to disposingthe solution.
 2. The method according to claim 1, further comprisingdraining the solution off the conductive surface of the workpiece byallowing the solution to flow through drain channels in at least some ofthe separable sweepers.
 3. The method according to claim 1, whereinelectrochemically mechanically processing is electrochemicallymechanically depositing a conductor onto the conductive surface.
 4. Themethod according to claim 1, wherein electrochemically mechanicallyprocessing is electrochemically mechanically polishing conductivematerial from the conductive surface.
 5. The method according to claim1, wherein each of the plurality of contact regions has a top surfacethat is rounded, such that a top rounded portion of each of the roundedcontact regions together form the substantially planar contact area. 6.The method according to claim 1, wherein each of the plurality ofcontact regions has a top surface that is triangular, such that a topedge portion of each of the triangular contact regions together form thesubstantially planar contact area.
 7. The method of according to claim1, further comprising contacting an electrode with the solution whilerelative movement and physical contact exist between the top surface ofthe workpiece surface influencing device and the conductive surface ofthe workpiece.
 8. The method of according to claim 1, further comprisingproviding an electrical connection to the conducting material through anexposed area of the conducting material to enable the conductingmaterial to operate as a cathode or an anode.
 9. A method ofelectrochemical mechanical processing a conductive surface of aworkpiece using an electrolyte, comprising: flowing the electrolytethrough channels in a workpiece surface influencing device onto theconductive surface of the workpiece; electrochemically mechanicallyprocessing the conductive surface in the presence of the electrolytewhile sweeping the conductive surface with the top surface of aworkpiece surface influencing device, wherein the top surface of theworkpiece surface influencing device is an insulating material thatcoats another material having raised regions and recessed regions. 10.The method of claim 9, wherein the raised regions comprise separablesweep elements.
 11. The method of claim 10, further comprising slidingat least one separable sweep element into a groove on the top surface ofthe workpiece surface influencing device.
 12. The method of claim 10,further comprising draining electrolyte off the conductive surface ofthe workpiece through a drain channel in at least one separable sweepelement.
 13. The method of claim 9, wherein the insulating material is aceramic.
 14. The method of claim 9, further comprising contacting anelectrode with the electrolyte while sweeping the conductive surface ofthe workpiece.
 15. The method of claim 9, wherein electrochemicallymechanically processing comprises electrochemically mechanicallydepositing conductive material onto the conductive surface.
 16. Themethod of claim 9, wherein electrochemically mechanically processingcomprises electrochemically mechanically removing conductive materialfrom the conductive surface.
 17. The method of claim 9, wherein theanother material is a ceramic material.
 18. The method of claim 9,wherein the another material is a conducting material.